I have had no issues with my transmission, 188k miles. After driving about 8 miles in over 90 degree temps the trans was not engaging. RPM's went up but the trans was as if it was not engaging. After parking for a few hours I was able to drive again with no slipping issues at all. the trans engaged in all gears.After approx 5 miles it began to rev and not move again. I never experienced this with any other bad transmission. Fluid is full with no burning smell with a proper color. Ideas??

Thanks,
Mike

The AW30 is an electronic auto transmission. When it gets (real) hot sometimes the solenoid sensors don't work.
If you do a flush of the oil- you REALLY need to take the pan off and change the filter screen-
but that may not help- it may be that the solenoids have to be replaced- only way to determine is to have them tested- but they are difficult to find if they do need to be replaced. - I couldn't find them here in Northern Calif. I bought from a company in China that manufactures them.
Anyway good luck.

Sounds like it is slipping when hot. Happened on an 850 of mine. Are you using synthetic ATF? Worth trying a full flush with cheap fluid, clean screen (if you have one) and refill with synthetic ATF.
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Will I buy another Volvo??? We'll see....